Authorities have a clearer picture as to why a Wilton building went up in flames.

It happened Tuesday at a commercial building on Danbury Road.

Officials say a contractor was preparing to do roofing work and apparently made a mistake gassing up a hot piece of equipment.

"He was filling up a gasoline-fed blower, to blow the stuff off the roof to get it ready and he filled a hot machine," says Wilton Fire Chief Ronald Kanterman. "We always tell people, don't fill your lawn mower when it's hot, when it's running, this is a classic case of that." 

No one was injured.

The roof has some damage, but the building's interior wasn't affected.